Question is how do you maintain your level?
I took JLPT 3 in 2003, (failed, but only because of my lacklustre attempt at learning kanji), but even speaking with my girlfriend everyday I've lost so much, (I'm realising that now I'm due to take the test again in a matter of weeks!!!).

Well, you maintain it any way you can. Read, speak, write, listen. Those are the four 'magic keys' to success. If you want your Japanese to grow along the 'JLPT scale' (let's call it) then I suggest you get test books for the JLPT, or textbooks which the JLPT sort of bases itself off of. Popular ones that teach grammar in a bit of a patterned manner (instead of just teaching yourself whatever you come across) are:
* Japanese For Busy People* Genki* Youkoso* Nakama

No one can really tell you HOW to maintain your Japanese... you have to find your own path, grasshopper. (: